Using cut/awk/sed with two different delimiters

Not sure what you're really doing with this but your could do it like so with sed:

$ sed 's/\(case\).*\(@test.com\)/\1\2/' 87529.txt 
[email protected]
[email protected]
[email protected]

This effectively trims everything out between case and the @.

You can do something similar with awk:

$ awk -F@ '{split($1,a,"_"); print a[1]"@"$2}' 87529.txt 

Also can be done with perl (similar to evilsoup's approach):

$ perl -p -e 's/_.*@/@/g' 87529.txt 

Or you can make use of perl's lookahead facility:

$ perl -p -e 's/_.*(?=@)//g' 87529.txt 

NOTE: Lookahead and lookbehind's in perl allow you to include strings in the regex pattern that you're matching on, without having them be included in the operation that will be performed against the regex. Think of them as dynamic versions of the caret (^) - beginning of a line, and dollar ($) - end of the line. This a little less hacky then having to add the @ back in, after removing it.

If your shell supports parameter expansion, you can do something like

while read line; do
    printf "%s\n" "${line%%_*}@${line#*@}"
done < your_file_here

The expansion ${line%%_*} removes the leftmost _ and everything following it while the expansion ${line#*@} removes the leftmost @ and everything preceding it.

If the lines may contain more than one @:

sed 's/^\([^@_]*\)_[^@]*@/\1@/'

Or:

awk -F@ -vOFS=@ 'NF >= 2 {sub(/_.*/,"",$1)};1'

Evilsoup's solution seems to be perfect!

Yet another solution using both sed and awk.

sed 's/_/ /g; s/@/ /g' file_name | awk '{ print $1"@"$NF '}

This would not exactly count for efficiency, but may be simple to understand, perhaps, when one does not want to mess with regular expressions. The above code does the following:

• The first pattern of sed replaces "_" with a blank.
• The second pattern of sed replaces "@" with a blank. So, now we contents of the file separated into multiple columns:

case test.com
case 1_2 test.com
case 1 test.com

• Finally, awk simply prints the first and last columns of the separated contents. Here, NF is a special symbol in awk that gives the number of fields in a row.

Here's another gawk way:

gawk -F_ '{if(NF>1){print $1$NF} else {print $NF}}'

Using _ as a field delimiter, we tell gawk to print the first and last fields if there are more than one field and the last field if there is only a single field.